For all those how have made a mistaken purchase - like I just did - you can return a Kindle book within fourteen days using the following steps....
To return a Kindle book:
Go to Manage Your Content and Devices (https://www.amazon.co.uk/mycd)
From Your Content, select the Actions button next to the title you want to return and then select Return for Refund.
In the pop-up window, select Return for Refund.
For all those who have the heart stopping moment of pressing the wrong button!